The first bismuth selenite fluoride, BiFSeO3, was obtained by aliovalent substitution of 2D BiOIO3. Its structure features a 3D network composed of 1D [BiF](2+) chains interconnected by SeO3 groups. BiFSeO3 exhibits a very strong second harmonic generation (SHG) effect of about 13.5 times that of KH2PO4 (KDP) under 1064 nm laser radiation and 1.1 times that of KTiOPO4 (KTP) under 2.05 μm laser radiation, which is the highest among all of the metal selenites reported. It has also very simple chemical composition and can be synthesized easily under mild hydrothermal conditions.
All-inorganic CsPbI3 perovskite quantum dots (QDs) have
attracted intense attention for their successful application in photovoltaics
(PVs) and optoelectronics that are enabled by their superior absorption
capability and great photoluminescence (PL) properties. However, their
photostability remains a practical bottleneck and further optimization
is highly desirable. Here, we studied the photostability of as-obtained
colloidal CsPbI3 QDs suspended in hexane. We found that
light illumination does induce photodegradation of CsPbI3 QDs. Steady-state spectroscopy, X-ray diffraction, Fourier transform
infrared spectroscopy, transmission electron microscopy, and transient
absorption spectroscopy verified that light illumination leads to
detachment of the capping agent, collapse of the CsPbI3 QD surface, and finally aggregation of surface Pb0. Both
dangling bonds containing surface and Pb0 serve as trap
states causing PL quenching with a dramatic decrease of PL quantum
yield. Our work provides a detailed insight about the correlation
between the structural and photophysical consequences of the photodegradation
process in CsPbI3 QDs and may lead to the optimization
of such QDs toward device applications.
A lead-free double-halide perovskite with a well-defined structure was synthesized, likely providing a new candidate material for eco-friendly optoelectronic devices.
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